"Writers," Joan Didion observed in 1968, "are always selling somebody out." It's one of those classic Didion statements, epigrammatic yet personal, a line that unpacks itself the more we consider what it implies. Didion may have been referring to journalism when she wrote that in the preface to "Slouching Towards Bethlehem," but she was also, as directly as can be imagined, addressing herself. "My only advantage as a reporter is that I am so physically small, so temperamentally unobtrusive, and so neurotically inarticulate that people tend to forget that my presence runs counter to their best interests. And it always does," she acknowledged earlier in the same paragraph, and it is this clarity, this edge of laser-sharp engagement, that sets her apart. For nearly 50 years now, her work has been defined by what she calls "triangulation," which is a way of explaining how she asserts herself in a piece of writing — to tell a reader where she is.

This question of presence, of triangulation, has come up on a Thursday afternoon in Didion's comfortably cluttered Upper East Side living room because she is discussing her new book, "Blue Nights" (Alfred A. Knopf: 188 pp., $25), which, she is saying, she almost didn't write. "There came a time," she recalls, her voice a low murmur, "when I decided I would simply repay the money I had gotten from Knopf. I told Lynn Nesbit that this was my plan, that I was going to tell Sonny I couldn't do it, and we would repay him. And Lynn said, 'Why don't you wait on that awhile?'"

Didion laughs softly at the idea of her agent, Nesbit, returning an advance to Knopf editor in chief Sonny Mehta, but at the center of the story, her discomfort is real. "Blue Nights" is a follow-up to her memoir "The Year of Magical Thinking," which, built around the mantra "Life changes fast.Life changes in the instant," describes the aftermath of two very personal tragedies: the death of her husband, John Gregory Dunne, of a heart attack in December 2003, and the extended illness of their daughter Quintana, who died at 39 in August 2005, just before the book came out. In this new work, Didion tries to tell Quintana's story, intercut with reflections on aging (she'll turn 77 in December) and what she worries is a diminishment of her creative power.

"I was having a terrible time with it at first," she continues, "because I didn't want to talk about Quintana for a lot of reasons. I didn't want to talk about her because I didn't want to talk about her. And the second reason was I didn't know if I had the right to talk about her. It was her life, not mine. So that got in the way for a long time." What's at issue here, in an apartment full of family photos and mementos, is permission, or maybe it's that, after all this time, Didion has become the reporter who triangulates herself. That's the challenge, and the risk, of memoir, and if she has always been a personal writer, with her last three books — "Blue Nights," "The Year of Magical Thinking" and 2003's "Where I Was From,"which she thinks of as "the California book" — she has shifted focus, in large measure, from the outer to the inner world.

At the heart of these three efforts is a sense of family; or better yet, a sense of place. In "Where I Was From," that place is physical, whereas in the later books it becomes psychological; still, for all intents and purposes, the perspective is the same. "The books are similar in that they ask more questions than they answer," Didion says. And yet, with each, she has zeroed in more tightly, moving from a subjective portrait of California to her husband and now to her child.

"In a certain way," she notes of "Blue Nights," " 'Magical Thinking' was more generalized; it's a whole different tone. I decided that maybe I ought to do something really personal, that I hadn't done anything really personal in 'Magical Thinking,' and maybe it was time to try." That's an unexpected observation: How much more personal can you get than to trace the death of a husband, the disruption of a family? But as is often true of Didion, there's an undercurrent beneath the surface of the words.

"I hadn't dealt with Quintana," she suggests. "I had dealt with her to some extent in the play" — Didion adapted "The Year of Magical Thinking" for the stage in 2007, as a one-woman show starring Vanessa Redgrave — "but the play [was] a … way of preserving myself at a distance. Because as I say in the book, watching that play on 45th Street at night was one moment during the day when Quintana did not necessarily die."

What Didion's talking about is narrative, which is, she understands, an inadequate consolation — "sentimental," she calls it in her 1989 essay "Pacific Distances" — although, perhaps, the only consolation we have. "We tell ourselves stories in order to live," she begins "The White Album," then undercuts the sentiment almost immediately: "Or at least we do for a while." Implicit in those lines is a recognition of the fundamental friction between the shaping impulses of literature and the chaos of the world. "It's just a tension you never resolve," Didion explains, eyes pale, unwavering. "I think I was writing 'Democracy' [her 1984 novel] when it came to me that, as well as I might describe the palm trees, it wasn't going to get me anywhere."

That's especially true of "Blue Nights," which, by its nature, cannot help but remain unresolved. Like "The Year of Magical Thinking," it's an example of the book as coping mechanism, of an author using language to "maintain movement," as Didion puts it, "otherwise you couldn't function. It's a necessary mask." Like "The Year of Magical Thinking," it is written almost entirely in fragments, as if it would otherwise be impossible to make all these impressions coalesce. "Memories are what you no longer want to remember," Didion writes about a third of the way through the book, and it's one of those lines that resonates because it hints at both the futility and the inescapability of the task. "A big part of the book is how to function. It's a lesson on how to function," she says flatly. "Because otherwise you would not be able to get through the day, the week."

For Didion, this is the point of nonfiction, even (or especially) when it cuts so close. She hasn't published a novel since "The Last Thing He Wanted" in 1996; for some time, she made notes for another but set them aside after Dunne's death. "Nonfiction," she insists, "is more personal for me. It's more personal in that it's more direct, and actually it's always been more direct, even when I first started doing pieces. I could talk more directly in a nonfiction voice than I could in fiction." In any case, she adds, "I'm not sure I have the physical strength to undertake a novel," although in the next instant, she is remarking again on the difficulty of writing "Blue Nights," a theme she also raises in the book. "All I know now," she declares there, "is that writing … no longer comes easily to me" — a statement that echoes her admission in "Slouching Towards Bethlehem" "that there is always a point in the writing of a piece when I sit in a room literally papered with false starts and cannot put one word after another and imagine that I have suffered a small stroke." The more things change, in other words, the more they never do.

And so, on this Thursday afternoon in her living room, Didion continues to work it through. "Let me try again to talk to you directly," she writes in "Blue Nights," speaking to her readers as if the book were a kind of intimacy. And: "I tell you this story just to prove that I can." There it is, that push to tell, to observe, and then the deepening: "That my frailty has not yet reached a point at which I can no longer tell a true story." Here again, Didion is triangulating, positioning herself, commenting on the inability of narrative to sustain us even as she invokes it just the same. Or, as she puts it, surrounded by all her familiar photographs: "I didn't think I'd get through this book. But I did. You always do."

Critics often write as if there were two Shirley Jacksons: one, the agoraphobic addict who penned weird tales like "The Haunting of Hill House"; the other, the humorous chronicler of family life in "Life Among the Savages." "Let Me Tell You" shows them to be emphatically the same woman.